Friday's tour bus crash in Union Square, which has left six people still hospitalized and four of those in critical condition, may have been the result of substandard maintenance and a mechanical failure on the bus itself, as the SFPD and subsequently Supervisor Jane Kim have now suggested publicly. The investigation into the crash is ongoing, but as CBS 5 reports, Kim is already pointing to the tour bus company as being at fault, and not the driver, who himself was hospitalized after the crash.

The bus was operated by City Sightseeing, a company that the Chronicle reports had their operating permit revoked for unknown reasons in 2013, though it is apparently valid today. A second City Sightseeing bus that ended up parallel to the one that lost control was also involved and hit with flying debris. (And, incidentally, this is the same company that that tour guide worked for who went on that infamous racist rant through Chinatown last year.)

Tour bus companies are regulated by the state, and Kim is suggesting that local regulatory authority could be helpful in preventing future incidents. "I think there are questions about ... record-keeping... and also ... how vehicles are being maintained by many of these very large tour bus companies regulated by the state," Kim said to CBS 5.

The CHP is currently reviewing the bus's maintenance records.

The wife of the bus driver told ABC 7 over the weekend that he believed that brake failure was to blame.

20 people were injured in the crash after the open-top bus knocked down scaffolding at the new Apple Store at Union Square, and also collided with a cyclist two blocks prior (on the 500 block of Post), who remains in critical condition.

Two other men and one woman are in critical condition, and two others remain in serious condition. Injuries reportedly include facial and head injuries, as well as damage to internal organs. The Chronicle says that none of the tour bus passengers were badly injured, and the worst injuries were sustained by those in cars hit by the bus, the cyclist, and one pedestrian. The bus driver and tour guide were also hurt.